Okay, so we are going by actual amount (i.e., mass) of fat tissue only?
Hmm.
First, we must consider whether SNORLAX is actually made of normal animal parts, because he looks like just a giant smooth fake thing. Upon further review I realized that SNORLAX posses the ability to use THICK FAT. Clearly then, both The Blob and SNORLAX can be assumed to consist of actual fat.
SNORLAX height is listed 2.1 m. He's roughly a circle so that puts his approximate volume at 3.6 m³.
The Blob's height is 5'10" or 1.78 m. I think he's also about a circle (a little taller than thick for body, but adding the limbs evens that out) so his volume is 2.2 m³.
SNORLAX weighs 1014.1 lbs.
The Blob weighs 510 lbs (not using gravity field power).
SNORLAX density is thus 1014.1 lbs/3.6 m³ = 282 lbs/m³.
Blob density is 510 lbs/2.2 m³ = 232 lbs/m³.
Looks like SNORLAX is undeniably fatter.